Characterization of microbial particle release from biomass and building material surfaces for inhalation exposure risk assessment

A conceptual approach including measurements of materials at rest (step 1), measurements using a large rotating drum (step 2) or a Particle-FLEC (step 2) and measurements at a workplace (step 4) has been used to characterize the release of microbial components (bacteria, fungi, actinomycetes, endotoxin or enzymes) and particles from straw, wood chips or fungal cultures of different ages on gypsum boards. Repeated agitation or handling periods were included in step 2 and step 4. There was a low similarity between the amount of microbial components measured in step 1 and the aerosolized amount (step 2) from gypsum boards, wood chips and straw. Ratios between some microbial components measured at the workplace (step 4) and measured in step 2, showed similarities. Less than 1.3% of the total amount of microorganisms and endotoxin becomes airborne during 5 min of agitation of straw or wood chips. Most microbial components were released at higher rates during the first agitation period than during the following periods. However, differences were seen between different microbial components, and endotoxin from straw was released at the same rate in two successive agitation periods. Fungal particles smaller than spores were released from fungal colonized gypsum boards at amounts that were up to 30 times higher in the first agitation period compared with that in the following period, while fungal spores were released at amounts that were five times as high in the first period compared with that in the following period. In addition to differences between microbial components, the release patterns of microbial components were different for wood chips and straw. The time for maximum particle release to half particle release was longer for straw than for wood chips. The observation that some components, e.g. endotoxin, are released at the same rate in two successive handling steps, and that others (e.g. fungi) are mainly released initially, shows that the exposure period to different components from the same material differs in duration. The observed differences in the release patterns of different components and the differences between materials are important when preventive steps are to be taken, and it stresses the importance of applying a relevant sampling time and period in exposure assessments.     

Exposure to airborne microbial components in autumn and spring during work at Danish biofuel plants

Exposure to microbial components can cause respiratory problems. The exposure levels to microbial components at biofuel plants are not known. Therefore, exposure to inhalable airborne fungi, bacteria, actinomycetes, endotoxin and NAGase was measured using personal and stationary samplers at five Danish biofuel plants in autumn and spring. The personal exposure levels to endotoxin (median=55 EU m-3), thermophilic actinomycetes (median=1.3x10(4) colony forming units (cfu) m-3), total bacteria (median=48x10(4) cells m-3) and total fungi (median=21x10(4) spores m-3) were, in general, high at the five biofuel plants. At straw reception areas, higher exposure to most microbial components was found in spring than in autumn. Endotoxin was found in higher concentrations at straw plants than at wood-chip plants, while the opposite was measured for Aspergillus fumigatus. Some tasks were associated with exposures to microorganisms and endotoxins at much higher levels than the suggested occupational exposure limits. For example, people working with a straw shredder for at least 30 min during a working day were exposed to a median endotoxin exposure of 23,775 endotoxin units (EU) m-3. People working with estimating the water content in wood chips and repairing the chips cranes for at least 30 min during a working day were exposed to a median value of A. fumigatus of 6.7x10(4) cfu m-3 and a median value of fungi of 70x10(4) spores m-3. Consequently, this working environment may cause respiratory disorders in the people working at the plant. Differences in exposure levels were seen between the plants and this may partly be due to differences of the process equipment, tasks and the biofuel handled.     

Assessment of bioaerosols and inhalable dust exposure in Swiss sawmills

An assessment of wood workers' exposure to airborne cultivable bacteria, fungi, inhalable endotoxins and inhalable organic dust was performed at 12 sawmills that process mainly coniferous wood species. In each plant, samples were collected at four or five different work sites (debarking, sawing, sorting, planing and sawing cockpit) and the efficiency of sampling devices (impinger or filter) for determining endotoxins levels was evaluated. Results show that fungi are present in very high concentrations (up to 35 000 CFU m(-3)) in all sawmills. We also find that there are more bioaerosols at the sorting work site (mean +/- SD: 7723 +/- 9919 CFU m(-3) for total bacteria, 614 +/- 902 CFU m(-3) for Gram-negative, 19 438 +/- 14 246 CFU m(-3) for fungi, 7.0 +/- 9.0 EU m(-3) for endotoxin and 2.9 +/- 4.8 g m(-3) for dust) than at the sawing station (mean +/- SD: 1938 +/- 2478 CFU m(-3) for total bacteria, 141 +/- 206 CFU m(-3) for Gram-negative, 12 207 +/- 10 008 CFU m(-3) for fungi, 2.1 +/- 1.9 EU m(-3) for endotoxin and 0.75 +/- 0.49 mg m(-3) for dust). At the same time, the species composition and concentration of airborne Gram-negative bacteria were studied. Penicillinium sp. were the predominant fungi, while Bacillus sp. and the Pseudomonadacea family were the predominant Gram-positive and Gram-negative bacteria encountered, respectively.     

Effects of personal exposures on pulmonary function and work-related symptoms among sawmill workers

Three green mills and two dry mills were studied for personal exposure to wood dust and biohazards associated with wood dust and their correlation to lung function and work-related symptoms among sawmill workers. The levels of exposure to endotoxin, (1-->3)-beta-D-glucan, bacteria and fungi were high in green mills compared with dry mills. Compared with dry mill workers, green mill workers had significantly high prevalence of regular cough, chronic bronchitis, regular blocked nose, regular sneezing, sinus problems, flu-like symptoms, and eye and throat irritation. Significant positive correlations were found among endotoxin and Gram (-)ve bacteria, (1-->3)-beta-D-glucan and fungi, and endotoxin and (1-->3)-beta-D-glucan exposure levels. Significant dose-response relationships were found for personal exposures and lung function, and lung function and work-related respiratory symptoms. The significant correlations found for respirable fractions show that not only inhalable but also respirable fractions are important in determining potential health effects of exposure to wood dust. The management and employees of the sawmilling industry should be educated on the potential health effects of wood dust. Wood dust should be controlled at the source.     

Exposure assessment to alpha- and beta-pinene,delta(3)-carene and wood dust in industrial production of wood pellets

The main aim of the study was to measure the exposure to monoterpenes (alpha- and beta-pinene and Delta(3)-carene) and wood dust during industrial production of wood pellets and briquettes. Additional aims were to compare the results from wood dust sampled on a filter with real time measurements using a direct reading instrument and to identify peak exposures to dust. Twenty-four men working at six companies involved in industrial production of wood pellets and briquettes participated in the study. Monoterpenes were measured by diffusive sampling and wood dust was measured as total dust. A data logger (DataRAM) was used for continuous monitoring of dust concentration for 18 of the participants. The sampling time was approximately 8 h. The personal exposure to monoterpenes ranged from 0.64 to 28 mg/m(3) and a statistically significant (Kruskal-Wallis test, P = 0.0002) difference in levels of monoterpenes for workers at different companies was seen. In the companies the personal exposure to wood dust varied between 0.16 and 19 mg/m(3) and for 10 participants the levels exceeded the present Swedish occupational exposure limit (OEL) of 2 mg/m(3). The levels of wood dust during the morning shift were significantly (Mann-Whitney test, P = 0.04) higher compared with the afternoon shift. Continuous registration of dust concentration showed peak values for several working operations, especially cleaning of truck engines with compressed air. For 24 workers in six companies involved in industrial production of wood pellets the personal exposure to monoterpenes was low and to wood dust high compared with the present Swedish OEL and previous studies in Swedish wood industries. Since the DataRAM can identify critical working tasks with high wood dust exposure a reduction in exposure levels could probably be achieved by changes in working routines and by the use of protective equipment.     

Sampling of high amounts of bioaerosols using a high-volume electrostatic field sampler

For studies of the biological effects of bioaerosols, large samples are necessary. To be able to sample enough material and to cover the variations in aerosol content during and between working days, a long sampling time is necessary. Recently, a high-volume transportable electrostatic field sampler for collection of fine particles has been described. The aim of this study was to investigate whether this sampler can be used for collection of high amounts of authentic bioaerosols that can subsequently be used for biological analysis. The investigation was carried out at a biofuel plant in a straw storage room and in a boiler room over two seasons. The sampled dust was quantified in terms of mass and characterized regarding microbial components and compared with dust sampled by Gravikon and GSP samplers. For the electrostatic field sampler, a prefilter was used to remove large objects. The prefilter was characterized for particle penetration and this testing indicated that the prefilter did not remove particles up to 10 mum, and therefore respirable dust was sampled by the electrostatic field sampler. Using the electrostatic field sampler in the straw storage and in the boiler room, 330 and 315 mg dust (net recovery of the lyophilized dust) was sampled during a period of 7 days, respectively. The sampling rates of the electrostatic field samplers were between 1.34 and 1.96 mg dust per hour, the value for the Gravikon was between 0.083 and 0.108 mg dust per hour and the values for the GSP samplers were between 0.0031 and 0.032 mg dust per hour. The standard deviations of replica samplings and the following microbial analysis using the electrostatic field sampler and GSP samplers were at the same levels. The exposure to dust in the straw storage was 7.7 mg m(-3) when measured by the electrostatic field sampler and 11.8 mg m(-3) when measured by the GSP inhalable dust sampler. The quantity (amount per mg dust) of total fungi, Aspergillus fumigatus, total bacteria, endotoxin and mesophilic actinomycetes sampled by the electrostatic field samplers and the Gravikon samplers varied within the same season by a factor smaller than four. The quantities of some microbial components were higher in the dust collected with all samplers in March than in August. In conclusion, by using the electrostatic field sampler, it was possible to sample replicas of large authentic aerosol samples that can be used, e.g. biological analysis.     

Airborne dust, ammonia, microorganisms, and antigens in pig confinement houses and the respiratory health of exposed farm workers

This study investigated the environmental conditions on pig farms and the respiratory health of pig farmers and their immunological response to airborne contaminants. Airborne concentrations of dust and ammonia were measured in 20 pig houses; viable microorganisms, endotoxins, and aeroallergens were measured in 6 of these houses, chosen to represent the range in dustiness. The 29 farmers employed on the farms completed a questionnaire and underwent lung function tests; 24 of them provided blood samples for the measurement of specific IgE and IgG antibody to extracts of pig squames and urine, feed components, and bacterial isolates. Mean airborne dust and ammonia concentrations in the pig houses ranged from 1.66 to 21.04 mg/m3 and from 1.50 to 13.23 ppm, respectively. Factors affecting these concentrations include time of year, feed systems used, and levels of ventilation. There was no direct relationship between airborne dust and ammonia concentrations. Airborne microorganisms ranged from 10(5) to more than 10(7) colony-forming units (cfu)/m3; most were bacteria, with few fungi or thermophilic actinomycetes isolated. Gram-positive bacterial genera (Staphylococcus, Micrococcus, and Bacillus spp.) predominated. Concentrations of endotoxin in collected airborne dust were low. Work-related respiratory symptoms, typically chest tightness/wheeze and nasal and eye irritation, were reported by 23 of the 29 workers. Three farmers had specific IgE to pig squames or urine and eight to feed components but none to the microbial extracts. Specific IgG to pig squames or urine and to feed components was demonstrated in 14 and 9 workers, respectively. Specific IgE responses occurred mainly in subjects with chest tightness or wheeze, although specific IgG responses were not related to symptoms.(ABSTRACT TRUNCATED AT 250 WORDS)     

Reduction potential of microbial, odour and ammonia emissions from a pig facility by biofilters

The intention of this study was the determination of the potential to reduce specific microbial bioaerosol (cultivable bacteria and fungi, total cell counts of microbes, airborne endotoxins and microbial volatile organic compounds, MVOC), odour and ammonia emissions from a pig facility by biofilters. Five identical biofilter units in half technical scale were filled with different filter materials (Biochips, coconut-peat, wood-bark, pellets + bark and compost) and connected in parallel to a piggery. The results showed obvious differences between the filter materials. Numbers of airborne cultivable bacteria were decreased by ca. 70 to 95% and the total counts of bacterial cells from ca. 25 to (>) 90%. The total amount of fungal cells was reduced by at least 60%, although the percentage of cultivable moulds in the air after passing the filters was sometimes higher than before. Airborne endotoxins and MVOC were effectively reduced by all filter materials to at least 90%. Regarding odour, the average reduction was between 40 and 83%, whereas only one of the filters proved to be capable of slightly reducing the ammonia emissions. No relationships between odour/ammonia and microbial bioaerosols with regard to the reduction efficiency of the different filter materials or the total load of the emitted air could be established. A tendency could be shown, that biofilters best capable to reduce odour emitted slightly more airborne bacteria, both cultivable and total cell counts.     

Personal exposure of dairy workers to dust,endotoxin, muramic acid,ergosterol, and ammonia on large-scale dairies in the high plains Western United States

Dairy workers experience a high degree of bioaerosol exposure, composed of an array of biological and chemical constituents, which have been tied to adverse health effects. A better understanding of the variation in the magnitude and composition of exposures by task is needed to inform worker protection strategies. To characterize the levels and types of exposures, 115 dairy workers grouped into three task categories on nine farms in the high plains Western United States underwent personal monitoring for inhalable dust, endotoxin, 3-hydroxy fatty acids (3-OHFA), muramic acid, ergosterol, and ammonia through one work shift. Eighty-nine percent of dairy workers were exposed to endotoxin at concentrations exceeding the recommended exposure guidelines (adjusted for a long work shift). The proportion of workers with exposures exceeding recommended guidelines was lower for inhalable dust (12%), and ammonia (1%). Ergosterol exposures were only measurable on 28% of samples, primarily among medical workers and feed handlers. Milking parlor workers were exposed to significantly higher inhalable dust, endotoxin, 3-OHFA, ammonia, and muramic acid concentrations compared to workers performing other tasks. Development of large modern dairies has successfully made progress in reducing worker exposures and lung disease prevalence. However, exposure to endotoxin, dust, and ammonia continues to present a significant risk to worker health on North American dairies, especially for workers in milking parlors. This study was among the first to concurrently evaluate occupational exposure to assayable endotoxin (lipid A), 3-hydroxy fatty acids or 3-OHFA (a chemical measure of cell bound and noncell-bound endotoxins), muramic acid, ergosterol, and ammonia among workers on Western U.S. dairies. There remains a need for cost-effective, culturally acceptable intervention strategies integrated in OHS Risk Management and production systems to further optimize worker health and farm productivity.     

Home characteristics as predictors of bacterial and fungal microbial biomarkers in house dust

Background

Measurement of fungal and bacterial biomarkers can be costly, but it is not clear whether home characteristics can be used as a proxy of these markers, particularly if the purpose is to differentiate specific classes of biologic exposures that have similar sources but may have different effects on allergic disease risk.

Objective

We evaluated home characteristics as predictors of multiple microbial biomarkers, with a focus on common and unique determinants and with attention to the extent of their explanatory ability.

Methods

In 376 Boston-area homes enrolled in a cohort study of home exposures and childhood asthma, we assessed the relationship between home characteristics gathered by questionnaire and measured gram-negative bacteria (GNB) (endotoxin and C10:0, C12:0, and C14:0 3-hydroxy fatty acids), gram-positive bacteria (GPB) (N-acetyl muramic acid), and fungal biomarkers [ergosterol and (1→6) branched, (1→3) β-d glucans] in bed and family room dust.

Results

Home characteristics related to dampness were significant predictors of all microbial exposures; water damage or visible mold/mildew in the home was associated with a 20–66% increase in GNB levels. Report of cleaning the bedroom at least once a week was associated with reduced GNB, GPB, and fungi. Presence of dogs or cats predicted increases in home bacteria or fungi. The proportion of variance in microbial biomarkers explained by home characteristics ranged from 4.2% to 19.0%.

Conclusions

Despite their associations with multiple microbial flora, home characteristics only partially explain the variability in microbial biomarker levels and cannot substitute for specific microbial measurements in studies concerned with distinguishing effects of specific classes of microbes.     

Heterogeneity in microbial exposure in schools in Sweden, Poland and Jordan revealed by analysis of chemical markers

We used gas chromatography--tandem mass spectrometry to analyze microbial components in 85 samples of airborne dust from schools in Jordan, Sweden, and Poland. To collect the samples, we allowed dust to settle on plexiglass plates hanging in the breathing zone in school buildings during both summer and winter. In each of the three countries, we conducted such sampling in two schools: one in an urban environment and the other in rural surroundings. The microbial marker profiles differed significantly between the schools and seasons. For example, samples from Jordan contained remarkably low levels of ergosterol (marker of fungal biomass) and high levels of 3-hydroxy acids (markers of lipopolysaccharide) of 10, 12, and 14 carbon chain lengths relative to such acids of 16 and 18 carbons in comparison with samples from Sweden and Poland. This dissimilarity in 3-hydroxy fatty acid distribution indicates significant differences in the populations of Gram-negative bacteria. We also noted that muramic acid (marker of bacterial biomass) exhibited the smallest variation between schools and seasons. In summary, our results demonstrate that exposure to microorganisms in indoor air in school buildings may differ markedly between countries, between seasons, and between urban and rural environments.     

Exposure to wood dust and endotoxin in small-scale wood industries in Tanzania

Workers in small-scale wood industries (SSWI) have increased risks of developing asthma and other respiratory diseases. Wood dust and microbial agents have both been suggested to play a role, but few studies have measured endotoxin exposure in SSWI in Africa. We assessed inhalable dust levels in 281 samples from 115 workers and bacterial endotoxins levels in 157 samples from 136 workers from SSWI in Dar es Salaam, Tanzania. The overall geometric mean of personal exposure was 3.3 mg/m(3); geometric standard deviation (GSD) 2.5; range 0.45-67.0 mg/m(3)) and 91 EU/m(3) (GSD 3.7; range 9-4914.8 EU/m(3)) for wood dust and endotoxins, respectively. Dust and endotoxin levels were weakly correlated (r = 0.44, n = 157, P < 0.0001). Between- and within-worker variances and percentages explained by the differences among job titles and seasons were 0.31 (9%) and 0.35 (30%), respectively, for wood dust exposure, and 0.35 (0%) and 0.35 (38%) for endotoxin exposure. Higher dust and endotoxin exposure levels were observed in the dry compared to the wet season, after correcting for differences in exposure between jobs. Carving and manual cleaning were associated with the highest dust exposures. Sewing seat covers and manual cleaning were associated with the highest endotoxin exposures. Dust and endotoxin exposure levels in SSWI are high and appropriate control measures are necessary.     

Airborne endotoxin associated with particles of different sizes and affected by water content in handled straw

High exposures to endotoxin are observed in environments where organic materials are handled and lower exposures are found in e.g. indoor air. Inhaled endotoxin contributes significantly to the induction of airway inflammation and dysfunction. The size of an inhaled particle influences the deposition in the airways and the following health symptoms. The objective is to characterise the distribution of endotoxin on airborne particles of different sizes in straw storage halls with high exposure and in other environments with lower exposure levels to endotoxin. Furthermore we have studied the influence of water content of handled straw on the size distribution of endotoxin containing particles. Total, inhalable, thoracic and respirable endotoxin and particles have each been quantified in aerosols from boiler rooms and straw storage halls at 24 power plants, including 21 biofuel plants. Inhalable, thoracic and respirable endotoxin have been quantified in aerosols from offices and outdoor air. The endotoxin concentration was higher in airborne thoracic dust than in airborne ‘total dust’. The median respirable fraction in the straw storage halls, boiler rooms at biofuel plants, boiler rooms at conventional plants, offices and outdoors was respectively 42%, 9%, 19%, 24% and 34%. Thoracic endotoxin per number of thoracic particles was higher than respirable endotoxin per number of respirable particles at the biofuel plants. In straw storage halls the fraction of endotoxin of respirable size was highest on the days with lowest water content in the received straw. Furthermore the exposures to all endotoxin fractions were highest on days with the lowest water content in the received straw. In conclusion the highest exposures and concentrations of endotoxin occur or tend to occur from thoracic dust. A high variation in endotoxin concentrations and in fractions of respirable or thoracic size is found in the different working areas. This is important in the risk assessment and makes attempts to influence the endotoxin exposure a possibility. Water content in straw affected the concentration, exposure level and size distribution of airborne endotoxin.     

The influence of bedding materials on bio-aerosol exposure in dairy barns

Bio-aerosol is a well-known cause of respiratory diseases. Exposure to bio-aerosols has been reported previously in dairy barns, but little is known about the sources of bio-aerosol. Bedding materials might be a significant source or substrate for bio-aerosol exposure. The aim of this study was to explore bio-aerosol exposure levels and its determinants in dairy barns with various bedding materials. Dust samples were collected at dairy barns using various bedding materials. Samples were analyzed for endotoxin and β(1 → 3)-glucan contents. Culturable bacteria and fungi were sampled by the Anderson N6 impactor. Exposure models were constructed using linear mixed models. The personal exposure levels to dust, endotoxin, and β(1 → 3)-glucan differed significantly between the barns utilizing diverse main bedding types (P<0.05), with the highest levels (GM: dust, 1.38 mg/m(3); endotoxin, 895 EU/m(3); β(1 → 3)-glucan, 7.84 μg/m(3)) in barns with compost bedding vs the lowest in barns with sawdust bedding (GM: dust, 0.51 mg/m(3); endotoxin, 183 EU/m(3); β(1 → 3)-glucan, 1.11 μg/m(3)). The exposure levels were also highly variable, depending on various extra bedding materials applied. Plant materials, particularly straw, utilized for bedding appeared to be a significant source for β(1 → 3)-glucan. Compost was significantly associated with elevated exposure levels. Between-worker variances of exposure were highly explained by determinants of exposure like type of bedding materials and milking by robot, whereas determinants could explain to lesser extent the within-worker variances. Exposure levels to endotoxin, β(1 → 3)-glucan, bacteria, and fungi in dairy barns were substantial and differed depending on bedding materials, suggesting bedding material types as a significant predictor of bio-aerosol exposure.     

Size distribution of particulate and associated endotoxin and bacteria in traditional swine barn rooms and rooms sprinkled with oil

The objective of this pilot study was to investigate if a once-a-day sprinkling of canola oil in a swine confinement facility alters the airborne concentration and distribution of particulate matter and associated compounds (endotoxin and culturable microbes). Particulate was collected using an eight-stage cascade impactor in four identical swine grower/finisher rooms of a swine barn. Particulate (mg/m(3)) and endotoxin (EU/m(3) and EU/mg) distribution was determined. A six-stage viable cascade impactor was used to quantify total bacteria, enteric bacteria, and fungi. Microbes were characterized from subcultures prepared from the 10 most predominant colony types on each stage 3 (aerodynamic size 3.3-4.7μm) of the collection plates. Results indicated that oil sprinkling reduced total dust by 86% and total endotoxin concentration by 82.5%. However, the distribution patterns indicate that reduction is observed predominantly on large dust particles. In addition, the proportion of endotoxin associated with smaller particulate sizes (i.e., particles <4.7 μm) was higher in the oil-sprinkled rooms. Oil sprinkling does not markedly alter distribution of total bacteria, enteric bacteria, or fungi. The most frequently identified species were gram-positive genera. Oil sprinkling in swine confinement grower/finisher rooms can significantly reduce airborne total dust and endotoxin; however, smaller particles and associated endotoxin appear to remain in suspension, suggesting the overall improvement in air quality is uncertain. Further distribution studies and exposure outcome studies would need to be undertaken to determine the impacts of oil sprinkling.     

Size Distribution of Particulate and Associated Endotoxin and Bacteria in Traditional Swine Barn Rooms and Rooms Sprinkled With Oil

ABSTRACT

The objective of this pilot study was to investigate if a once-a-day sprinkling of canola oil in a swine confinement facility alters the airborne concentration and distribution of particulate matter and associated compounds (endotoxin and culturable microbes). Particulate was collected using an eight-stage cascade impactor in four identical swine grower/finisher rooms of a swine barn. Particulate (mg/m³) and endotoxin (EU/m³ and EU/mg) distribution was determined. A six-stage viable cascade impactor was used to quantify total bacteria, enteric bacteria, and fungi. Microbes were characterized from subcultures prepared from the 10 most predominant colony types on each stage 3 (aerodynamic size 3.3–4.7μm) of the collection plates. Results indicated that oil sprinkling reduced total dust by 86% and total endotoxin concentration by 82.5%. However, the distribution patterns indicate that reduction is observed predominantly on large dust particles. In addition, the proportion of endotoxin associated with smaller particulate sizes (i.e., particles <4.7 μm) was higher in the oil-sprinkled rooms. Oil sprinkling does not markedly alter distribution of total bacteria, enteric bacteria, or fungi. The most frequently identified species were gram-positive genera. Oil sprinkling in swine confinement grower/finisher rooms can significantly reduce airborne total dust and endotoxin; however, smaller particles and associated endotoxin appear to remain in suspension, suggesting the overall improvement in air quality is uncertain. Further distribution studies and exposure outcome studies would need to be undertaken to determine the impacts of oil sprinkling.     

Monitoring of bacterial pathogens at workplaces in power plant using biochemical and molecular methods

Purpose

The aim of this study was to characterize the ways of spreading of the most common bacterial species isolated from workers as well as from the air and raw materials at the workplaces in power plant utilizing biomass sources. To monitor microbial transmission and identify the source of contamination in the working environment, a combination of molecular and biochemical methods was applied.

Methods

The study was carried out at workplaces in power plant utilizes biomass as a main fuel source. At each of the studied workplaces, bioaerosol particles were collected on sterile Teflon filters using personal conical inhalable samplers (CIS), and biomass samples (straw pellets and briquettes, corn briquettes, sunflower pellets and wood chips) were directly taken from their storage places. Simultaneously with that, the swab samples from the hands of ten workers and their used respiratory masks (of FFP2 class) were also collected after the work shift to evaluate individual workers’ microbial contamination. In all collected samples, total bacterial concentrations were assessed and the most common microbial isolates were identified to the species level using both biochemical (API tests) and molecular polymerase chain reaction (PCR), followed by random amplification of polymorphic DNA (RAPD) typing methods.

Results

The mean concentrations of culturable bacteria in the air and in biomass samples at the studied workplaces were high, i.e. 1.2?×?10⁶cfu/m³ and 3.8?×?10⁴cfu/g, respectively. The number of bacteria in the swab and mask samples also reached a high level of 1.4?×?10⁴ cfu/ml and 1.9?×?10³ cfu/cm², respectively. Among the most frequently isolated microorganisms from all types of samples were Gram-positive bacteria of the genus Bacillus and Staphylococcus xylosus. 37 bacterial strains belonging to the genus Bacillus (B. licheniformis 8, B. pumilus 15 and B. subtilis 4) and Staphylococcus (10) were genotyped by the RAPD-PCR method. Based on RAPD-PCR analyses, the genomic similarity among 19 Bacillus strains isolated from biomass, air, protective mask and hand samples as well as 6 S. xylosus strains isolated from air, mask and hand samples exceeded 80%.

Conclusion

This study demonstrated that biomass is the primary source of bacteria at power plant workplaces. These results also revealed that biomass-associated bacteria can be easily transferred to workers’ hands and mask during their routine activities. To improve health protection at the workplaces, adequate training courses on hand hygiene and how to use and remove respiratory masks correctly for workers should be introduced as a key element of the prevention strategy. From the occupational point of view, the PCR-based methods seem to be an efficient tool for a fast and precise typing of bacterial strains isolated from different sources in the occupational environment. Such methods may help to implement appropriate prophylactic procedures and minimize transmission of infectious agents at workplaces.

     

Occupational exposure to organic dust associated with municipal waste collection and management

The aim of the study was to assess the occupational exposure of workers employed in the municipal waste collection and management industry. Air samples were collected in the workers' breathing zone; two samples were collected parallely. The assessment concerned exposure to organic dust, endotoxins, bacteria and fungi. The questionnaire data showed that workers found themselves in good or very good health. They also regarded noise, dustiness, odor, physical effort and changeable atmospheric conditions as the most strenuous factors. The highest dust concentrations were observed on the sites of waste collection (mean, 7.7 mg/m3) and composting (mean, 4.6 mg/m3). Samples collected on the composting site contained the largest amount of endotoxins (mean concentration, 76 ng/m3). This was followed by sorting facility (61 ng/m3) and waste collection area (36 ng/n3). Gram-negative rods (primarily intestinal) were found in all samples collected at workposts, which justified the adoption of the air concentrations of endotoxins as a criterion for assessing their hygienic conditions. Taking MAC for total suspended dust (4.0 mg/m3) and the concentration of 10 ng/m3 for endotoxin as the criteria for the exposure evaluation, it must be considered that waste collectors and composting site workers are working in poor hygienic conditions. Workers employed at the most hazardous workposts did not use personal protective equipment (glasses, antirespirators), thus infringing a fundamental condition for limiting health hazards (Directive 2000/54/EC).     

Exposure to microbes, endotoxins and total dust in cigarette and cigar manufacturing: an evaluation of health hazards

The concentrations of airborne microbes, endotoxins and total dust were measured in one cigar and two cigarette factories in order to evaluate the risk of respiratory symptoms. The role of humidifiers as a source of microbes was investigated. Air samples for the analyses were collected near workers' breathing zones during different phases of production. Gram-negative bacteria, mesophilic fungi, thermotolerant fungi and thermophilic actinomycetes, but not Aspergillus glaucus fungi, were found in higher concentrations in the cigar factory than in the cigarette factories. High microbe concentrations (10(4)-10(5)cfu m(-3)) occurred throughout the production line in the cigar factory. The highest dust and endotoxin concentrations were found in the wick-making department in the cigar factory (3.3mg dust per m(3) and 38ng endotoxin per m(3)) and during the weighing or handling of raw tobacco in the cigarette factories (4.5 mg dust per m(3) and 106ng endotoxin per m(3)). The spray humidifiers in the cigar factory were a more important source of microbes than was raw tobacco. In the cigarette factories, steam humidifiers were used; the humidified air was free of microbes. The microbe concentrations in the tobacco factories were lower than in environments known to have caused allergic alveolitis.     

The application of dustiness tests to the prediction of worker dust exposure

Laboratory bench tests, known as dustiness tests, have been used to evaluate and compare the potential of various powders to cause occupational dust exposure. Dustiness tests are used to develop products with reduced dust emissions. The correlation between dustiness test results and dust exposures was evaluated at two bag dumping and bag filling operations. At one bag dumping and one bag filling operation, there was evidence of a relationship between dustiness test results and dust exposures. In one case, regression analysis showed that dust exposures could be predicted to within nearly one order of magnitude. The variability in this prediction was caused by the inherent variability in the occupational dust exposures. In the other case, there was evidence of a correlation after the data had been adjusted for the effect of varying drop height. At the remaining two operations, no correlation between dust exposures and dustiness test results were observed. These results indicate that the relevance of dustiness tests to occupational dust exposure needs to be evaluated at each site. Because a better option does not exist, manufacturers should continue to use empirical dustiness tests to develop better products in the laboratory. The conclusions reached in the laboratory need to be validated by dust exposure measurements in the field, however.